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Aquatic feed extrusion has seen many changes in the last decade for a variety of reasons. Formulation changes, physical characteristics of the feed and higher production rates are just a few of the changes the industry has endured. Two specialized equipment processes, the PDU® and SAS®, were developed by Extru-Tech, Inc. to specifically address problems encountered in aquatic feed manufacturing. Although these processes are not brand new, they continue to be utilized in new applications around the world.

SABETHA, KS. March 2013— Maintaining their industry leadership role in food and product safety, Extru-Tech recently completed an industry-first scientific validation study that used a production-scale extruder to prove extrusion's effectiveness in controlling Salmonella in dry pet food. In effect, Extru-Tech’s scientific validation, which was conducted at the company’s Level 2 Bio-Safety Extrusion Lab in Manhattan, Kansas, proved the kill/lethality step of the extrusion system as an effective control against the persistent pathogen.

Since 2010, the Food and Drug Administration has had a zero tolerance policy for Salmonella, which is why the pet food industry has experienced a dramatic increase in recalls over the past few years. However, even though every manufacturer strives for products that are 100 percent pathogen free, applicable and validated scientific studies to support properly designed pet food safety systems weren’t possible … until now.

To this point, petfood manufacturers have relied on traditional lab studies based on testing equipment ranging from beakers and pressure pots to table-top model extruders. Moreover, most testing has been completed at very low production rates of 30 grams to a few kilograms per hour. In contrast, Extru-Tech configured a BSL-2 pilot plant outfitted with an E525 production-scale extrusion system, capable of producing nearly 8,000 pounds of product per hour, and the equipment was configured for the production of an industry-generic, low-moisture, dry-expanded pet food. The selected formula was then charged with a three-serotype cocktail of Salmonella, an inoculant that represents typical contamination events in the manufacturing process.

As part of the study, Extru-Tech also considered the fact that a dry inoculant introduced into the ingredient stream better represents how the pathogens are usually present within contaminated raw ingredients. If Salmonella is in a liquid, which is often the case in research studies, heat will transfer quickly and kill it

quickly. However, this is not a representation of what happens in a petfood plant, and creates a false set of operational parameters that do not control Salmonella.

“Extru-tech is using actual equipment that you would find in most pet food plants in a bio-hazard laboratory or a pilot plant,” said Jim Marsden, PhD, regents distinguished professor at Kansas State University. “Raw materials can be inoculated with Salmonella or other pathogens and the effect of the extrusion process can be exactly quantified. This process is a breakthrough for the pet food industry.”

All three replications of the challenge study resulted in a log reduction of Salmonella that exceeded the 5-log reduction requirement of a CCP allocation. Extru-Tech also discovered that many readily available and scientific methods of inoculation rendered a result that was not truly representative of a contamination event because of the method by which the raw material was inoculated.

“Extru-tech is documenting the parameters that are required to deactivate Salmonella in the extrusion process,” said Dr. Marsden. “There are other production steps that follow where Salmonella could re-contaminate the product. Consequently, Extru-tech is looking at those additional steps to identify interventions that could be applied downstream to prevent recontamination.”

Extru-Tech, Inc., headquartered in Sabetha, Kansas, currently produces and markets one of the industry's most complete lines of extrusion processing systems, along with a full line of ancillary equipment and customized equipment solutions for specialized processes. Since 1985, Extru-Tech has installed extrusion systems worldwide, designed for the production of human food, pet food, aquatic feed and animal feed products.